diff --git a/reme2/component/base_component.py b/reme2/component/base_component.py
index 4cab9f58..7b7c122e 100644
--- a/reme2/component/base_component.py
+++ b/reme2/component/base_component.py
@@ -1,7 +1,7 @@
 """Base class for components."""
 
 import asyncio
-from abc import ABC, abstractmethod
+from abc import ABC
 from typing import TYPE_CHECKING
 
 from ..enumeration import ComponentEnum
diff --git a/reme2/component/file_store/bm25_lite.py b/reme2/component/file_store/bm25_lite.py
new file mode 100644
index 00000000..c81a206f
--- /dev/null
+++ b/reme2/component/file_store/bm25_lite.py
@@ -0,0 +1,273 @@
+"""Lightweight BM25 search engine with persistent index support.
+
+BM25Lite implements the Okapi BM25 ranking algorithm for text retrieval.
+It uses an inverted index for efficient document lookup and supports
+incremental updates, persistence via pickle, and automatic vocab compaction.
+"""
+
+import math
+import pickle
+from collections import Counter
+from pathlib import Path
+from typing import TypedDict
+
+from ..base_component import BaseComponent
+from ..tokenizer import BaseTokenizer
+from ...enumeration import ComponentEnum
+
+
+class DocMeta(TypedDict):
+    """Document metadata stored in the index.
+
+    Attributes:
+        len: Number of tokens in the document.
+        token_ids: Set of unique token IDs present in the document.
+    """
+    len: int
+    token_ids: set[int]
+
+
+class BM25Lite(BaseComponent):
+    """Lightweight BM25 search engine with file-based persistence.
+
+    BM25 (Best Matching 25) is a probabilistic ranking function that scores
+    documents based on term frequency and document length normalization.
+
+    Attributes:
+        k1: Term frequency saturation parameter (default: 1.5).
+        b: Document length normalization parameter (default: 0.75).
+        vocab: Token to token ID mapping.
+        inverted_index: Token ID to {doc_id: term_frequency} mapping.
+        doc_meta: Document ID to metadata mapping.
+
+    Args:
+        index_dir: Directory to store index files.
+        k1: BM25 term frequency saturation parameter.
+        b: BM25 document length normalization parameter.
+        tokenizer: Name of tokenizer component to use.
+    """
+
+    def __init__(
+            self,
+            index_dir: str | Path,
+            k1: float = 1.5,
+            b: float = 0.75,
+            tokenizer: str = "default",
+            **kwargs):
+        super().__init__(**kwargs)
+        self.k1 = k1
+        self.b = b
+        self.index_dir = Path(index_dir)
+        self.index_dir.mkdir(parents=True, exist_ok=True)
+        self.vocab: dict[str, int] = {}
+        self.inverted_index: dict[int, dict[str, int]] = {}
+        self.doc_meta: dict[str, DocMeta] = {}
+        self.total_len = 0
+
+        self._idf_cache: dict[int, float] = {}
+        self.tokenizer_name = tokenizer
+        self._tokenizer: BaseTokenizer | None = None
+
+    def clear(self):
+        """Reset the index to empty state."""
+        self.vocab = {}
+        self.inverted_index = {}
+        self.doc_meta = {}
+        self.total_len = 0
+        self._idf_cache = {}
+
+    @property
+    def n_docs(self) -> int:
+        """Number of indexed documents."""
+        return len(self.doc_meta)
+
+    @property
+    def avg_len(self) -> float:
+        """Average document length in tokens."""
+        return self.total_len / self.n_docs if self.n_docs > 0 else 0.0
+
+    @property
+    def index_file(self) -> Path:
+        """Path to the index pickle file based on tokenizer name."""
+        if self._tokenizer is None:
+            raise RuntimeError("Tokenizer not initialized. Call start() first.")
+        name = type(self._tokenizer).__name__.replace("Tokenizer", "").lower()
+        return self.index_dir / f"index_{name}.pkl"
+
+    async def _start(self) -> None:
+        """Initialize tokenizer and load existing index if available."""
+        if self.app_context is not None:
+            tokenizer_dict: dict = self.app_context.components.get(ComponentEnum.TOKENIZER, {})
+            if self.tokenizer_name in tokenizer_dict:
+                self._tokenizer = tokenizer_dict[self.tokenizer_name]
+
+        if self._tokenizer is None:
+            from ..tokenizer import RegexTokenizer
+            self._tokenizer = RegexTokenizer(filter_stopwords=False)
+
+        if self._tokenizer is not None:
+            await self._tokenizer.start()
+
+        if self.index_file.exists():
+            await self.load()
+            self.logger.info(f"Loaded index from {self.index_dir}")
+
+    async def _close(self) -> None:
+        """Save index and cleanup tokenizer on shutdown."""
+        if self.inverted_index:
+            await self.dump()
+            self.logger.info(f"Saved index to {self.index_dir}")
+
+        if self._tokenizer is not None:
+            await self._tokenizer.close()
+
+    def _tokenize(self, text: str) -> list[str]:
+        if self._tokenizer is None:
+            raise RuntimeError("Tokenizer not initialized. Call start() first.")
+        return self._tokenizer.tokenize([text])[0]
+
+    def _tokens_to_ids(self, tokens: list[str]) -> list[int]:
+        ids = []
+        for token in tokens:
+            token = token.strip()
+            if token:
+                ids.append(self.vocab.setdefault(token, len(self.vocab)))
+        return ids
+
+    def add_docs(self, docs_dict: dict[str, str]):
+        """Index or update multiple documents.
+
+        Args:
+            docs_dict: Mapping of document ID to document content.
+        """
+        for doc_id, content in docs_dict.items():
+            if doc_id in self.doc_meta:
+                self._remove_doc(doc_id)
+
+            tokens = self._tokenize(content)
+            if not tokens:
+                continue
+
+            token_ids = self._tokens_to_ids(tokens)
+            token_counts = Counter(token_ids)
+
+            for tid, tf in token_counts.items():
+                self.inverted_index.setdefault(tid, {})[doc_id] = tf
+
+            self.doc_meta[doc_id] = {"len": len(token_ids), "token_ids": set(token_counts)}
+            self.total_len += len(token_ids)
+
+        self._idf_cache = {}
+
+    def reindex(self):
+        """Rebuild vocab to remove unused tokens and compact token IDs."""
+        # Collect all token IDs still in use
+        used_token_ids: set[int] = set()
+        for tid in self.inverted_index:
+            used_token_ids.add(tid)
+
+        if not used_token_ids:
+            self.clear()
+            return
+
+        # Build new vocab with compact IDs
+        old_to_new: dict[int, int] = {}
+        new_vocab: dict[str, int] = {}
+        for token, old_tid in self.vocab.items():
+            if old_tid in used_token_ids:
+                new_tid = len(new_vocab)
+                new_vocab[token] = new_tid
+                old_to_new[old_tid] = new_tid
+
+        # Rebuild inverted_index with new token IDs
+        new_inverted_index: dict[int, dict[str, int]] = {}
+        for old_tid, postings in self.inverted_index.items():
+            new_tid = old_to_new[old_tid]
+            new_inverted_index[new_tid] = postings
+
+        # Update doc_meta token_ids
+        for doc_id, meta in self.doc_meta.items():
+            meta["token_ids"] = {old_to_new[old_tid] for old_tid in meta["token_ids"] if old_tid in old_to_new}
+
+        self.vocab = new_vocab
+        self.inverted_index = new_inverted_index
+        self._idf_cache = {}
+
+    def _remove_doc(self, doc_id: str):
+        if doc_id not in self.doc_meta:
+            return
+        meta = self.doc_meta[doc_id]
+        self.total_len -= meta["len"]
+        for tid in meta["token_ids"]:
+            if tid in self.inverted_index:
+                self.inverted_index[tid].pop(doc_id, None)
+                if not self.inverted_index[tid]:
+                    del self.inverted_index[tid]
+        del self.doc_meta[doc_id]
+
+    def _get_idf(self, token_id: int) -> float:
+        if token_id in self._idf_cache:
+            return self._idf_cache[token_id]
+        df = len(self.inverted_index.get(token_id, {}))
+        self._idf_cache[token_id] = math.log(1 + (self.n_docs - df + 0.5) / (df + 0.5)) if df else 0.0
+        return self._idf_cache[token_id]
+
+    def retrieve(self, query: str, k: int = 3) -> dict[str, float]:
+        """Search for documents matching the query.
+
+        Args:
+            query: Search query string.
+            k: Maximum number of results to return.
+
+        Returns:
+            Dict mapping document IDs to BM25 scores, sorted by score descending.
+        """
+        query_ids = [self.vocab[t] for t in self._tokenize(query) if t in self.vocab]
+        if not query_ids or self.n_docs == 0:
+            return {}
+
+        scores: dict[str, float] = {}
+        avg_len = self.avg_len
+
+        for tid in query_ids:
+            if tid not in self.inverted_index:
+                continue
+            idf = self._get_idf(tid)
+            for doc_id, tf in self.inverted_index[tid].items():
+                doc_len = self.doc_meta[doc_id]["len"]
+                tf_score = tf * (self.k1 + 1) / (tf + self.k1 * (1 - self.b + self.b * doc_len / avg_len))
+                scores[doc_id] = scores.get(doc_id, 0.0) + idf * tf_score
+
+        return dict(sorted(scores.items(), key=lambda x: x[1], reverse=True)[:k]) if scores else {}
+
+    async def dump(self):
+        """Persist index to disk via pickle."""
+        with open(self.index_file, "wb") as f:
+            pickle.dump(
+                {
+                    "vocab": self.vocab,
+                    "inverted_index": self.inverted_index,
+                    "doc_meta": self.doc_meta,
+                    "total_len": self.total_len,
+                    "k1": self.k1,
+                    "b": self.b,
+                },
+                f,
+            )
+
+    async def load(self):
+        """Load index from disk. Clears index on failure."""
+        try:
+            with open(self.index_file, "rb") as f:
+                data = pickle.load(f)
+            self.vocab = data["vocab"]
+            self.inverted_index = data["inverted_index"]
+            self.doc_meta = data["doc_meta"]
+            self.total_len = data.get("total_len", 0)
+            self.k1 = data.get("k1", 1.5)
+            self.b = data.get("b", 0.75)
+            self._idf_cache = {}
+        except Exception as e:
+            self.logger.exception(f"Failed to load index: {e}")
+            self.index_file.unlink(missing_ok=True)
+            self.clear()
diff --git a/test/reme2/test_bm25_lite.py b/test/reme2/test_bm25_lite.py
new file mode 100644
index 00000000..a0921b05
--- /dev/null
+++ b/test/reme2/test_bm25_lite.py
@@ -0,0 +1,556 @@
+"""Tests for BM25Lite search engine."""
+
+import asyncio
+import tempfile
+from pathlib import Path
+
+import sys
+
+sys.path.insert(0, str(Path(__file__).parent.parent.parent))
+
+from reme2.component.file_store.bm25_lite import BM25Lite
+
+
+async def create_bm25(index_dir: Path, k1: float = 1.5, b: float = 0.75) -> BM25Lite:
+    """Create and start a BM25Lite instance."""
+    bm25 = BM25Lite(index_dir=index_dir, k1=k1, b=b)
+    await bm25.start()
+    return bm25
+
+
+def test_basic_init():
+    """Test BM25Lite initialization."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = BM25Lite(index_dir=tmpdir)
+            assert bm25.k1 == 1.5
+            assert bm25.b == 0.75
+            assert bm25.vocab == {}
+            assert bm25.inverted_index == {}
+            assert bm25.doc_meta == {}
+            assert bm25.n_docs == 0
+            assert bm25.avg_len == 0.0
+            print("✓ test_basic_init passed")
+
+    asyncio.run(run())
+
+
+def test_start_with_tokenizer():
+    """Test BM25Lite starts and initializes tokenizer."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+            assert bm25._tokenizer is not None
+            assert bm25.is_started
+
+            await bm25.close()
+            assert not bm25.is_started
+            print("✓ test_start_with_tokenizer passed")
+
+    asyncio.run(run())
+
+
+def test_add_single_doc():
+    """Test adding a single document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({"doc1": "hello world"})
+
+            assert bm25.n_docs == 1
+            assert bm25.total_len > 0
+            assert "doc1" in bm25.doc_meta
+
+            await bm25.close()
+            print("✓ test_add_single_doc passed")
+
+    asyncio.run(run())
+
+
+def test_add_multiple_docs():
+    """Test adding multiple documents."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                "doc1": "hello world",
+                "doc2": "hello python",
+                "doc3": "world python",
+            }
+            bm25.add_docs(docs)
+
+            assert bm25.n_docs == 3
+            assert len(bm25.vocab) > 0
+            assert len(bm25.inverted_index) > 0
+
+            await bm25.close()
+            print("✓ test_add_multiple_docs passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_basic():
+    """Test basic retrieval functionality."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                "doc1": "python programming language",
+                "doc2": "java programming language",
+                "doc3": "python data analysis",
+            }
+            bm25.add_docs(docs)
+
+            results = bm25.retrieve("python", k=3)
+            assert len(results) <= 3
+            assert "doc1" in results or "doc3" in results
+
+            await bm25.close()
+            print("✓ test_retrieve_basic passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_with_limit():
+    """Test retrieval with result limit."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                f"doc{i}": f"python programming {i}" for i in range(10)
+            }
+            bm25.add_docs(docs)
+
+            results = bm25.retrieve("python", k=3)
+            assert len(results) == 3
+
+            results = bm25.retrieve("python", k=5)
+            assert len(results) == 5
+
+            await bm25.close()
+            print("✓ test_retrieve_with_limit passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_empty_query():
+    """Test retrieval with empty or unknown query."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {"doc1": "hello world"}
+            bm25.add_docs(docs)
+
+            results = bm25.retrieve("", k=3)
+            assert results == {}
+
+            results = bm25.retrieve("unknownxyz", k=3)
+            assert results == {}
+
+            await bm25.close()
+            print("✓ test_retrieve_empty_query passed")
+
+    asyncio.run(run())
+
+
+def test_retrieve_empty_index():
+    """Test retrieval from empty index."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            results = bm25.retrieve("python", k=3)
+            assert results == {}
+
+            await bm25.close()
+            print("✓ test_retrieve_empty_index passed")
+
+    asyncio.run(run())
+
+
+def test_update_doc():
+    """Test updating an existing document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({"doc1": "hello world python"})
+            old_len = bm25.total_len
+
+            bm25.add_docs({"doc1": "java"})
+            assert bm25.n_docs == 1
+            assert bm25.total_len != old_len
+
+            results = bm25.retrieve("java", k=1)
+            assert "doc1" in results
+
+            await bm25.close()
+            print("✓ test_update_doc passed")
+
+    asyncio.run(run())
+
+
+def test_remove_doc():
+    """Test removing a document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                "doc1": "hello world",
+                "doc2": "hello python",
+            }
+            bm25.add_docs(docs)
+            assert bm25.n_docs == 2
+
+            bm25._remove_doc("doc1")
+            assert bm25.n_docs == 1
+            assert "doc1" not in bm25.doc_meta
+
+            results = bm25.retrieve("hello", k=2)
+            assert "doc1" not in results
+            assert "doc2" in results
+
+            await bm25.close()
+            print("✓ test_remove_doc passed")
+
+    asyncio.run(run())
+
+
+def test_remove_nonexistent_doc():
+    """Test removing a nonexistent document (should be no-op)."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({"doc1": "hello world"})
+            bm25._remove_doc("nonexistent")
+            assert bm25.n_docs == 1
+
+            await bm25.close()
+            print("✓ test_remove_nonexistent_doc passed")
+
+    asyncio.run(run())
+
+
+def test_clear():
+    """Test clearing the index."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({
+                "doc1": "hello world",
+                "doc2": "hello python",
+            })
+            assert bm25.n_docs == 2
+
+            bm25.clear()
+            assert bm25.n_docs == 0
+            assert bm25.vocab == {}
+            assert bm25.inverted_index == {}
+            assert bm25.doc_meta == {}
+            assert bm25.total_len == 0
+            assert bm25._idf_cache == {}
+
+            await bm25.close()
+            print("✓ test_clear passed")
+
+    asyncio.run(run())
+
+
+def test_reindex():
+    """Test reindex functionality to compact vocab."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({"doc1": "hello world"})
+            bm25._remove_doc("doc1")
+
+            assert bm25.n_docs == 0
+            assert len(bm25.vocab) > 0
+
+            bm25.reindex()
+            assert bm25.vocab == {}
+            assert bm25.inverted_index == {}
+
+            await bm25.close()
+            print("✓ test_reindex passed")
+
+    asyncio.run(run())
+
+
+def test_reindex_with_docs():
+    """Test reindex with remaining documents."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({
+                "doc1": "hello world",
+                "doc2": "hello python",
+            })
+
+            old_vocab = bm25.vocab.copy()
+            bm25._remove_doc("doc1")
+
+            bm25.reindex()
+
+            assert bm25.n_docs == 1
+            assert "doc2" in bm25.doc_meta
+            assert len(bm25.vocab) < len(old_vocab)
+
+            results = bm25.retrieve("hello", k=1)
+            assert "doc2" in results
+
+            await bm25.close()
+            print("✓ test_reindex_with_docs passed")
+
+    asyncio.run(run())
+
+
+def test_persistence():
+    """Test dump and load persistence."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            tmpdir_path = Path(tmpdir)
+
+            bm25 = await create_bm25(tmpdir_path)
+            docs = {
+                "doc1": "hello world",
+                "doc2": "hello python",
+                "doc3": "programming language",
+            }
+            bm25.add_docs(docs)
+
+            old_vocab = bm25.vocab.copy()
+            old_doc_meta = {k: dict(v) for k, v in bm25.doc_meta.items()}
+
+            await bm25.dump()
+            await bm25.close()
+
+            bm25_new = await create_bm25(tmpdir_path)
+
+            assert bm25_new.vocab == old_vocab
+            assert bm25_new.n_docs == 3
+            for doc_id, meta in old_doc_meta.items():
+                assert doc_id in bm25_new.doc_meta
+
+            results = bm25_new.retrieve("hello", k=2)
+            assert "doc1" in results or "doc2" in results
+
+            await bm25_new.close()
+            print("✓ test_persistence passed")
+
+    asyncio.run(run())
+
+
+def test_custom_params():
+    """Test custom k1 and b parameters."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir), k1=2.0, b=0.5)
+
+            assert bm25.k1 == 2.0
+            assert bm25.b == 0.5
+
+            bm25.add_docs({"doc1": "test document"})
+            results = bm25.retrieve("test", k=1)
+            assert "doc1" in results
+
+            await bm25.close()
+            print("✓ test_custom_params passed")
+
+    asyncio.run(run())
+
+
+def test_chinese_text():
+    """Test with Chinese text."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                "doc1": "我爱北京天安门",
+                "doc2": "北京是中国的首都",
+                "doc3": "上海的天气很好",
+            }
+            bm25.add_docs(docs)
+
+            results = bm25.retrieve("北京", k=2)
+            assert len(results) <= 2
+            assert "doc1" in results or "doc2" in results
+
+            await bm25.close()
+            print("✓ test_chinese_text passed")
+
+    asyncio.run(run())
+
+
+def test_mixed_chinese_english():
+    """Test with mixed Chinese and English text."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                "doc1": "Python 是一种编程语言",
+                "doc2": "Java 编程语言",
+                "doc3": "Python 数据分析",
+            }
+            bm25.add_docs(docs)
+
+            results = bm25.retrieve("Python", k=3)
+            assert len(results) > 0
+
+            results = bm25.retrieve("编程", k=2)
+            assert len(results) > 0
+
+            await bm25.close()
+            print("✓ test_mixed_chinese_english passed")
+
+    asyncio.run(run())
+
+
+def test_idf_cache():
+    """Test IDF cache functionality."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({
+                "doc1": "hello world",
+                "doc2": "hello python",
+            })
+
+            token = "hello"
+            if token in bm25.vocab:
+                tid = bm25.vocab[token]
+                idf1 = bm25._get_idf(tid)
+                assert tid in bm25._idf_cache
+                idf2 = bm25._get_idf(tid)
+                assert idf1 == idf2
+
+            await bm25.close()
+            print("✓ test_idf_cache passed")
+
+    asyncio.run(run())
+
+
+def test_avg_len():
+    """Test average document length calculation."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            assert bm25.avg_len == 0.0
+
+            bm25.add_docs({"doc1": "hello world python"})
+            assert bm25.avg_len > 0
+
+            bm25.add_docs({"doc2": "test"})
+            new_avg = bm25.avg_len
+            assert new_avg > 0
+
+            await bm25.close()
+            print("✓ test_avg_len passed")
+
+    asyncio.run(run())
+
+
+def test_score_ordering():
+    """Test that results are ordered by score descending."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            docs = {
+                "doc1": "python python python",
+                "doc2": "python python",
+                "doc3": "python",
+            }
+            bm25.add_docs(docs)
+
+            results = bm25.retrieve("python", k=3)
+            scores = list(results.values())
+
+            for i in range(len(scores) - 1):
+                assert scores[i] >= scores[i + 1]
+
+            await bm25.close()
+            print("✓ test_score_ordering passed")
+
+    asyncio.run(run())
+
+
+def test_empty_doc():
+    """Test adding empty document."""
+
+    async def run():
+        with tempfile.TemporaryDirectory() as tmpdir:
+            bm25 = await create_bm25(Path(tmpdir))
+
+            bm25.add_docs({"doc1": ""})
+            assert bm25.n_docs == 0
+
+            bm25.add_docs({"doc2": "   "})
+            assert bm25.n_docs == 0
+
+            await bm25.close()
+            print("✓ test_empty_doc passed")
+
+    asyncio.run(run())
+
+
+if __name__ == "__main__":
+    print("\n=== BM25Lite Tests ===")
+    test_basic_init()
+    test_start_with_tokenizer()
+    test_add_single_doc()
+    test_add_multiple_docs()
+    test_retrieve_basic()
+    test_retrieve_with_limit()
+    test_retrieve_empty_query()
+    test_retrieve_empty_index()
+    test_update_doc()
+    test_remove_doc()
+    test_remove_nonexistent_doc()
+    test_clear()
+    test_reindex()
+    test_reindex_with_docs()
+    test_persistence()
+    test_custom_params()
+    test_chinese_text()
+    test_mixed_chinese_english()
+    test_idf_cache()
+    test_avg_len()
+    test_score_ordering()
+    test_empty_doc()
+    print("\n所有测试通过!")
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